Durable multi-component antibiotic formulation for topical use

ABSTRACT

Disclosed are methods and formulations for the treatment or prevention of infections on mammalian tissues such as skin. Specifically, the methods of this invention involve the in situ formation of a polymeric cyanoacrylate film containing mixed antibiotics over mammalian tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/308,863 filed Aug. 1, 2001 which application isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

This invention is directed to methods and formulations for the treatmentor prevention of infections on mammalian tissues such as skin.Specifically, the methods of this invention involve the in situformation of a polymeric cyanoacrylate film containing mixed antibioticsover mammalian tissue.

REFERENCES

The following publications, patent applications and patents are cited inthis application as superscript numbers:

-   -   ¹ Barley, “Methods for Retarding Blister Formation by Use of        Cyanoacrylate Adhesives”, U.S. Pat. No. 5,306,490, issued Apr.        26, 1994.    -   ² Barley, et al., Methods for Treating Suturable Wounds by Use        of Sutures and Cyanoacrylate Adhesives, U.S. Pat. No. 5,254,132,        issued Oct. 19, 1993    -   ³ McIntire, et al., Process for the Preparation of Poly        (α-Cyanoacrylates), U.S. Pat. No. 3,654,239, issued Apr. 4, 1972    -   ⁴ Barley, et al., Methods for Treating Non-Suturable Wounds by        Use of Cyanoacrylate Adhesives, U.S. Pat. No. 6,342,213, issued        Jan. 29, 2002.    -   ⁵ Barley, et al., Methods for Reducing Skin Irritation From        Artificial Devices by Use of Cyanoacrylate Adhesives, U.S. Pat.        No. 5,653,789, issued Aug. 5, 1997    -   ⁶ Tighe, et al., Methods for Inhibiting Skin Ulceration by Use        of Cyanoacrylate Adhesives, U.S. Pat. No. 5,403,591, issued Apr.        4, 1995    -   ⁷ Tighe, et al., for Use of Cyanoacrylates for Providing a        Protective Barrier, U.S. Pat. No. 5,580,565, issued Dec. 6, 1996    -   ⁸ Askill, et al., for Methods for Draping Surgical Incision        Sites, U.S. Pat. No. 5,807,563 issued Sep. 15, 1998    -   ⁹ Greff, et al., for Cyanoacrylate Compositions Comprising an        Antimicrobial Agent, U.S. Pat. No. 5,684,042, issued Nov. 3,        1997

All of the above publications, patent applications and patents areherein incorporated by reference in their entirety to the same extent asif each individual publication, patent application or patent wasspecifically and individually indicated to be incorporated by referencein its entirety.

STATE OF THE ART

Many commercial topical antibiotic preparations exist in creams,lotions, petroleum bases, etc. While they are easily applied, they arealso easily rubbed off (e.g., ointments applied to the skin frequentlyrub off onto the patient's clothing within minutes or hours therebylosing their effectiveness). This problem is most commonly addressed byapplying protective layers or covers such as dressings over theointments.

The covers, while simple to use, can absorb the ointment or cause it todisplace to another area. The ointment can also prevent the adhesive onthe dressing from effectively adhering. In some cases, attempts havebeen made to incorporate the active ingredients in pre-formed films orin film-forming solutions. Unfortunately, most preformed films havelimited diffusion of the active ingredients and show little or noclinical activity.

Greff, et al.⁹ have demonstrated that certain iodophors can beincorporated into prepolymeric cyanoacrylate compositions to createstable film forming liquids wherein the iodophor effectively providesfor antimicrobial activity to the polymer film formed therefrom.However, many antimicrobial agents are incompatible with prepolymericcyanoacrylate compositions causing either immediate polymerization orpreventing polymerization from occurring at all or within a reasonableperiod of time after application to mammalian tissue. In addition, whileinsoluble antibiotics appear to cause less rapid effects on theperformance of the prepolymeric cyanoacrylate compositions, thesematerials will most frequently fall out of suspension and resistre-suspension. This is particularly disadvantageous where the mixingpotential is restricted by the size of the container, e.g., a single usepackage.

Heretofore, prepolymeric cyanoacrylate compositions have been disclosedfor use in a variety of medical environments such as an alternative oradjunct to sutures² or as a hemostat³. Other described uses ofcyanoacrylate prepolymers include their use on mammalian tissue to formpolymeric films which are utilized:

-   -   to prevent friction blister formation¹,    -   in treating small non-suturable wounds⁴,    -   in inhibiting surface skin irritation arising from friction        between the skin surface and artificial devices such as tapes,        prosthetic devices, casts, etc.⁵,    -   as surgical incise drapes⁸,    -   in inhibiting skin ulceration⁶, and    -   forming a protective film to inhibit skin degradation due to        incontinence.⁷

In each case, the combination of conventional antibiotics with thesecompositions would be useful particularly as a replacement forconventional bandages.

SUMMARY OF THE INVENTION

This invention is directed, in part, to polymerizable cyanoacrylatecompositions comprising one or more insoluble antibiotics. Inparticular, these compositions comprise a sufficient amount of athickening agent to form a stable suspension or gel. These compositionsare useful in methods for covering mammalian tissue with a polymericantibacterial film which reduces the risk of infection to the underlyingand/or adjacent tissue and, in the case of mamalian skin, forms awaterproof film over the skin.

This invention is also directed, in part, to methods for the treatmentor prevention of infections in mammalian tissue which methods involveformation of an antibacterial cyanoacrylate polymeric film overmammalian tissue by the in situ polymerization of the polymerizablecyanoacrylate composition. This composition can be applied as aliquid/gel to the skin surface and can include additional therapeuticagents such as analgesics, anti-inflammatory agents, and the like.

Accordingly, in one of its composition aspects, this invention isdirected to a polymerizable film-forming cyanoacrylate compositioncomprising:

-   -   from about 50 to 99 weight percent of a polymerizable        cyanoacrylate ester based on the total weight of the        composition;    -   an antibacterially effective amount of an antibiotic or mixture        of antibiotics which are insoluble in the polymerizable        cyanoacrylate ester; and    -   a sufficient amount of a thickening agent which forms a stable        suspension or gel in combination with the cyanoacrylate ester        and the antibiotic or the mixture of antibiotics.

Preferably, the antibiotic employs a mixture of antibiotics in order toprovide a full spectrum of activity and, more preferably, this mixtureis employed at from about 0.01 to about 2 weight percent based on thetotal weight of the composition.

Preferably, the thickening agent is employed in an amount ranging fromabout 0.5 to about 10 weight percent based on the total weight of thecomposition.

Accordingly, in another of its composition aspects, this invention isdirected to a film-forming cyanoacrylate composition comprising:

-   -   from about 50 to 99 weight percent of a polymerizable        cyanoacrylate ester based on the total weight of the        composition;    -   from about 0.01 to about 2 weight percent of a mixture of        antibiotics which are insoluble in the polymerizable        cyanoacrylate ester; and    -   from about 0.5 to about 10 weight percent of a thickening agent        which forms a stable suspension or gel in combination with the        cyanoacrylate ester and the mixture of antibiotics.

In one of its method aspects, this invention is directed to a method forthe treatment or prevention of infections on mammalian tissues whichmethod comprises:

-   -   (a) identifying bacterially infected mammalian tissue or tissue        at risk of such infection;    -   (b) applying to the mammalian tissue identified in (a) above a        sufficient amount of a composition comprising:    -   from about 50 to 99 weight percent of a polymerizable        cyanoacrylate ester based on the total weight of the        composition;    -   an antibacterially effective amount of an antibiotic or mixture        of antibiotics which are insoluble in the polymerizable        cyanoacrylate ester; and    -   a sufficient amount of a thickening agent which forms a stable        suspension or gel in combination with the cyanoacrylate ester        and the antibiotic or the mixture of antibiotics; and    -   (c) polymerizing the cyanoacrylate ester so as to form an        adherent polymeric film on the tissue-where the composition was        applied.

Preferably, the polymerizable cyanoacrylate ester comprises an esterwhich, in monomeric form, is represented by formula I:

where R is selected from the group consisting of:

-   -   alkyl of 1 to 10 carbon atoms,    -   alkenyl of 2 to 10 carbon atoms,    -   cycloalkyl groups of from 5 to 8 carbon atoms,    -   phenyl,    -   2-ethoxyethyl,    -   3-methoxybutyl,    -   and a substituent of the formula:        -   wherein each R′ is independently selected from the group            consisting of:        -   hydrogen and methyl, and    -   R″ is selected from the group consisting of:        -   alkyl of from 1 to 6 carbon atoms,        -   alkenyl of from 2 to 6 carbon atoms,        -   alkynyl of from 2 to 6 carbon atoms,        -   cycloalkyl of from 3 to 8 carbon atoms,        -   aralkyl selected from the group consisting of benzyl,            methylbenzyl and phenylethyl,        -   phenyl, and        -   phenyl substituted with 1 to 3 substituents selected from            the group consisting of hydroxy, chloro, bromo, nitro, alkyl            of 1 to 4 carbon atoms, and alkoxy of from 1 to 4 carbon            atoms.

More preferably, in the cyanoacrylate esters of formula I, R is alkyl offrom 2 to 10 carbon atoms and more preferably alkyl of from 2 to 8carbon atoms. Even more preferably, R is butyl, pentyl or octyl and mostpreferably, R is n-butyl.

In another preferred embodiment, the polymerized cyanoacrylatecomposition has a thickness of no more than about 1 millimeter and, morepreferably, the polymer layer has a thickness of from about 2 to about500 microns and still more preferably from about 20 to about 100microns.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is directed to methods and formulations for the treatmentor prevention of infections on mammalian tissues such as skin. However,prior to discussing this invention in further detail, the followingterms will first be defined.

DEFINITIONS

As used herein, the following terms have the following meanings:

The term “polymerizable cyanoacrylate esters” refers to polymerizableformulations comprising cyanoacrylate monomers or polymerizableoligomers which, in their monomeric form, are preferably compoundsrepresented by formula I as described above.

More preferably, in formula I, R is an alkyl group of from 2 to 10carbon atoms including ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl,sec-butyl, n-pentyl, iso-pentyl, n-hexyl, iso-hexyl, 2-ethylhexyl,n-heptyl, octyl, nonyl, and decyl. More preferably, R is butyl, pentylor octyl and most preferably, R is n-butyl. Mixtures of such compoundscan also be employed as disclosed by Berger, et al., U.S. Pat. No.5,998,472 which is incorporated herein by reference in its entirety.

A preferred cyanoacrylate ester for use in the invention isn-butyl-2-cyanoacrylate.

The polymerizable cyanoacrylate esters described herein rapidlypolymerize in the presence of water vapor or tissue protein, and then-butyl-cyanoacrylate bonds to mammalian skin tissue without causinghistotoxicity or cytotoxicity.

Such polymerizable cyanoacrylate esters are sometimes referred to hereinas prepolymers and compositions comprising such esters are sometimesreferred to herein as prepolymer compositions.

Polymerizable cyanoacrylate esters are known in the art and aredescribed in, for example, U.S. Pat. Nos. 3,527,224; 3,591,676;3,667,472; 3,995,641; 4,035,334; and 4,650,826 the disclosures of eachare incorporated herein by reference in their entirety.

The term “biocompatible plasticizer” refers to any material which issoluble or dispersible in the cyanoacrylate composition, which increasesthe flexibility of the resulting polymeric film coating on the skinsurface, and which, in the amounts employed, is compatible with the skinas measured by the lack of moderate to severe skin irritation. Suitableplasticizers are well known in the art and include those disclosed inU.S. Pat. Nos. 2,784,127 and 4,444,933 the disclosures of both of whichare incorporated herein by reference in their entirety. Specificplasticizers include, by way of example only, acetyl tri-n-butylcitrate, acetyl trihexyl citrate, butyl benzyl phthalate, dibutylphthalate, dioctylphthalate, n-butyryl tri-n-hexyl citrate, diethyleneglycol dibenzoate, and the like. The particular biocompatibleplasticizer employed is not critical and preferred plasticizers includedioctylphthalate and C₂-C₄-acyl tri-n-hexyl citrates.

The term “thickening agent” refers to any biocompatible material whichincreases the viscosity of the composition. Suitable thickening agentsinclude, by way of example, polymethyl methacrylate (PMMA) or otherpreformed polymers soluble or dispersible in the composition, asuspending agent such as fumed silica and the like with PMMA beingpreferred. Fumed and modified fumed silica are particularly useful inproducing a gel for topical application having a viscosity of from about1,500 to about 1,000,000 centipoise at 20° C. Suitable thickening agentsfor the compositions described herein also include a partial polymer ofthe alkyl cyanoacrylate as disclosed in U.S. Pat. Nos. 3,654,239 and4,038,345 both of which are incorporated herein by reference in theirentirety.

Thickening agents are deemed to be biocompatible if they are soluble ordispersible in the composition and are compatible with the skin asmeasured by the lack of moderate to severe skin irritation.

The phrase “antibiotic or mixture of antibiotics which are insoluble inthe polymerizable cyanoacrylate ester” refers to those antibiotics whichindividually or in admixture have a solubility of less than 0.01 mg/mLof cyanoacrylate ester at 20° C. Suitable antibiotics include bacitracinzinc, polymyxin B sulfate, neomycin sulfate, and the like.

The term “stable suspension” refers to suspensions wherein at least 50percent, and preferably at least 90%, of the suspended material remainsin suspension for a period of at least 3 months and, preferably at least6 months, at 20° C.

Methods

The methods of this invention comprise the in situ formation of anantibacterial, cyanoacrylate polymer film on mammalian tissue such asmammalian skin.

The treatment protocol preferably involves tissue preparation prior toin situ formation of the cyanoacrylate polymer. For example, mammalianskin is first conventionally treated by the attending health careprofessional by cleaning with an appropriate antimicrobial composition.The skin is preferably dried, e.g., blotted dry, and then an adherentantibacterial polymeric film is formed over this site by applying acyanoacrylate composition of this invention. As noted above, thiscomposition comprises polymerizable cyanoacrylate monomers and/orreactive oligomers which, upon contact with the skin, polymerizes insitu to form a polymeric film. Pretreatment of other mammalian tissuewill also follow conventional procedures.

Polymerization occurs at ambient conditions for a sufficient period oftime to allow robust films to form. In general, the particular length oftime required for polymerization will vary depending on factors such asthe amount of adhesive composition applied, the temperature of thetissue, the moisture content of the tissue, the surface area of tissue,and the like. However, in a preferred embodiment, polymerization isgenerally complete within about 10 to about 60 seconds while the tissueis maintained at ambient conditions; however, in some cases,polymerization can occur up to about 5 minutes. During this period, thetissue is maintained in a position which permits the cyanoacrylate topolymerize and form a polymeric film while minimizing any movement whichmight dislodge the cyanoacrylate from the tissue or create undesirablebonding.

Sufficient amounts of the composition are employed to cover (i.e., coat)the entire tissue site with a layer of the cyanoacrylate polymer. Ifnecessary, excess cyanoacrylate monomer and/or oligomer can be removedwith a wipe or tissue paper before polymerization or, afterpolymerization, any polymer formed at unintended sites can be removedwith materials such as acetone.

After polymerization, the resulting polymeric film forms anantibacterial, barrier film which strongly adheres to the skin, isflexible and waterproof. Such strong adherence effectively eliminatesthe possibility that the film will separate from the tissue. In the caseof application to mammalian skin, the polymeric film will only adhere tothe skin for a period of about 1-4 days after which time it sloughs off.This occurs because the cyanoacrylate polymer is adhering only to theepidermal layer which is continuously in the process of being sloughedoff and replaced by the underlying cells. Accordingly, the cyanoacrylatefilm need not be removed from such skin.

The polymeric film should be maintained in an unbroken manner over theentire tissue. This can be assured by careful application of thecyanoacrylate adhesive onto the tissue. Additionally, the. use of aplasticizer will facilitate the maintenance of the polymeric film in anunbroken manner and will inhibit cracking of the film.

In one embodiment, after application of the initial polymeric layer, asecond, preferably thinner, layer is applied thereto. Additional amountsof cyanoacrylate composition can be applied as needed to maintain anunbroken coating covering over the tissue.

Application is conducted under conditions wherein the polymeric filmpreferably has a thickness of no more than about 1 millimeter and, morepreferably, the polymer layer has a thickness of from about 2 to about500 microns and still more preferably from about 20 to about 100microns. If thinner polymeric films are desired, then the polymeric filmshould have a thickness of from about 2 to about 50 microns andpreferably from 10 to 40 microns. The amount of cyanoacrylatecomposition applied to a unit area to obtain such thicknesses is wellwithin the skill of the art.

The size and thickness of the polymeric film formed onto the tissue areacan be readily controlled by the amount and viscosity of cyanoacrylateadhesive composition packaged in a single dose product or by use of amultiple use dispenser which governs the amount of material applied ontoa unit area of surface skin. In this regard, the dispenser described byOtake, U.S. Pat. No. 4,958,748, which is incorporated by reference inits entirety, is one example of a dispenser which dispenses thecyanoacrylate adhesive composition in a controlled dropwise manner.Other methods for the controlled dispersement of the cyanoacrylateadhesive include, by way of example, a spray applicator, brush, wipe,swab or solid paddle applicator, applicators for repeated andintermittent use of the cyanoacrylate composition and the like.

In applicators, the cyanoacrylate composition is stored at ambientconditions and can be provided in sterile form.

Compositions

The cyanoacrylate compositions comprising the polymerizablecyanoacrylate esters, the thickening agent(s) and the insolubleantibiotic(s) can be prepared by conventional methods of mixing theappropriate components until homogenous.

The concentration of polymerizable cyanoacrylate ester employed in thecomposition is preferably from about 50 to about 99 percent by weightbased on the total weight of the composition.

The concentration of thickening agent employed is preferably an amountsufficient to form a stable suspension or gel with the polymerizablecyanoacrylate ester and the antibiotic or mixture of antibiotics'. This,in turn, correlates with the viscosity of the composition. For example,stable suspensions of insoluble antibiotics are preferably achieved byaddition of sufficient thickening agent to provide for a viscosity offrom about 50 to 50,000 centipoise at 20° C. For gel forms, it ispreferred to add sufficient thickening agent into the composition toimpart a viscosity of from about 1,500 to about 1,000,000 centipoise at20° C. at zero shear. Preferably, the composition is thixotropic suchthat application of the composition to the tissue is significantlyenhanced.

In a particularly preferred embodiment, the composition will comprisefrom about 0.5 to about 10 percent by weight of the thickening agentbased on the total weight of the composition wherein the compositionwill have a viscosity of from about 50 to about 1,000,000 centipoise at20° C.

Still further, the concentration of the antibiotic or mixture ofantibiotics employed in the composition is sufficient to render theresulting polymeric film antibacterial. That is to say that theconcentration of the antibiotic or mixture of antibiotic in the film issufficient to ensure that the film exhibits antibacterial activity whenmeasured by conventional assays such as that described in Greff, et al.⁹In a preferred embodiment, the composition will comprise from about 0.01to about 2 percent by weight of the antibiotic or mixtures ofantibiotics based on the total weight of the composition.

The cyanoacrylate compositions preferably include a biocompatibleplasticizer and such plasticizers are preferably included in thecomposition from about 10 to 30 weight percent and more preferably fromabout 18 to 25 weight percent based on the total weight of thecomposition absent any antimicrobial agent.

Additionally, the cyanoacrylate compositions described herein preferablyinclude a polymerization inhibitor in an effective amount to inhibitpremature polymerization of the composition during storage. In aparticularly preferred embodiment, this inhibitor is sulfur dioxidewhich is employed at from about 50 to 500 ppm, preferably 200 to 500ppm, based on the total weight of the composition absent anyantimicrobial agent. Other preferred polymerization inhibitors includeglacial acetic acid, free radical inhibitors (e.g., hydroquinones) andthe like which can be used alone or in combination with SO₂.

The polymerizable cyanoacrylate ester compositions may additionallycontain one or more optional additives such as medicaments, colorants,perfumes, anti-diffusion agents, rubber modifiers, modifying agents,etc. In practice, each of these optional additives should be bothmiscible and compatible with the cyanoacrylate composition and theresulting polymer. Compatible additives are those that do not preventthe use of the cyanoacrylates in the manner described herein.

In general, colorants are added so that the polymer layer formed on theskin will contain a discrete and discernable color. Perfumes are addedto provide a pleasant smell to the formulation. Rubber modifiers areadded to further enhance the flexibility of the resulting polymer layer.Medicaments are added as necessary to achieve a desired prophylactic ortherapeutic effect. The amount of each of these optional additivesemployed in the composition is an amount necessary to achieve thedesired effect.

Other medicaments suitable for use in conjunction with the cyanoacrylatecomposition include corticoid steroids such as described by Greff, etal. in U.S. Pat. No. 5,962,010 which is incorporated herein by referencein its entirety and analgesic compounds such as lidocaine. The formerreduces inflammation at the tissue site whereas the latter reduces pain.Combinations of a steroid with an analgesic are also covered.

Utility

The methods described herein are useful in forming an antibacterialpolymeric film over mammalian tissue. This polymeric film findsparticular utility in treating an existing bacterial infection at thetissue site or in inhibiting this tissue from becoming infected withbacteria. Suitable mammals for use in these methods preferably includehumans as well as domestic animals such as horses, cows, dogs, sheep,cats, etc.

The following examples illustrate certain embodiments of the inventionbut is not meant to limit the scope of the claims in any way.

Example 1 below illustrates how the methods of this invention could bepracticed.

EXAMPLE 1

A man subject to recurrent skin infections presents himself to theattending clinician with a large area of the inner right thigh that isbeginning to redden and itch. The involved area and the surrounding twoinches of skin are coated with a gel composition comprising 70% n-butylcyanoacrylate, 23% di-ethylhexyl phthalate plasticizer, 6% hydrophobicfumed silica, 0.3% neomycin sulfate, 0.15% polymixin B sulfate, and0.55% bacitracin zinc (all percentages are weight percentages based onthe total weight of the composition). The gel spreads easily and setswithin 60 seconds to form a coherent flexible polymeric film.

From the foregoing description, various modifications and changes in thecomposition and method will occur to those skilled in the art. All suchmodifications coming within the scope of the appended claims areintended to be included therein.

1-11. (canceled)
 12. A method for the treatment or prevention ofinfections on mammalian tissues which method comprises: (a) identifyingbacterially infected mammalian tissue or tissue at risk of suchinfection; (b) applying to the mammalian tissue identified in (a) abovea sufficient amount of a composition comprising: from about 50 to 99weight percent of a polymerizable cyanoacrylate ester based on the totalweight of the composition; an antibacterially effective amount of anantibiotic or mixture of antibiotics which are insoluble in thepolymerizable cyanoarcylate ester; and a sufficient amount of thickeningagent which forms a stable suspension or gel in combination with thecyanoacrylate ester and the antibiotic or the mixture of antibiotics;and (c) polymerizing the cyanoacrylate ester so as to form an adherentpolymeric film to the tissue where the composition was applied.